Void fraction in bubbly and slug flow in downward two-phase flow in vertical and inclined wellbores

Much work has been done in the area of two-phase up-flow while the flow of gas and liquid in the downward direction has not received much attention. This paper presents a model for estimating void fraction in downward two-phase flow for vertical and inclined systems for the two dominant flow regimes, bubbly and slug flow. To model slip between the phases and the transition between the flow regimes, the drift-flux approach is adapted. The flowing mixture densities calculated from the model are useful for pressure gradient estimation. Extensive data gathered by Beggs, Mukherjee, and Kokal are used to validate the model. The data indicate that the effect of buoyancy, expressed by the terminal bubble rise velocity has the same magnitude as that for the case of up-flow for both bubbly and slug flow. In addition, the flow distribution parameter in bubbly flow appears to have the same value of 1.2 as in the case of up-flow. However, for slug flow, the flow parameter is represented by a somewhat lower value (1.12) than that for up-flow.

Void fraction in bubbly and slug flow in downward two-phase flow in vertical and inclined wellbores Conference Paper